The disposition of waste from the recycling of nuclear fuel is a major problem in the nuclear power industry. Currently, there are a variety of recycling schemes to recover key actinides and transform fission products into durable waste forms. Because of the creation of multiple waste streams, the UREX (Uranium Refining by EXtraction) method is no longer a viable system for actinide recovery and fission product separation. The PUREX (Plutonium Uranium Refining by EXtraction) process is currently used in many countries for recycling used nuclear fuel with the only other alternative for used fuel being direct storage in a geological repository. The PUREX method recovers and separates uranium (U) and plutonium (Pu) present in spent fuel. This method cannot be performed in the U.S. due to the separation of Pu which violates the non-proliferation agreement.
Used Nuclear Fuel (UNF) is extremely hazardous; consequently new advanced recycling technologies are pursued to limit the hazards of UNF. Specifically, technetium-99 (Tc-99) is of particular concern. As a pertechnatate ion, it is very mobile in the environment and has an extremely long half-life. Furthermore, cesium (Cs) and strontium (Sr)are heat generating nuclides and have short half-lives. Separation of these fission products will ultimately decrease the need for long term and short term storage in geological repositories.
The PUREX method contains a series of steps in order to extract and separate U and Pu from the fission product impurities. The first cycle decontaminates U and Pu from Americium (Am) and Curium (Cm), as well as other fission products. The second cycle extracts U and Pu into an organic phase containing tri-n butyl phosphate (TBP), The organic phase enters the fission product scrub section to remove fission product impurities. Pu is reduced to a lower oxidation state and stripped from U. The U and Pu products are further processed with additional cycles to purify the products. Other known technologies require separate techniques for separating other actinides from fission product impurities. For example, Am and Cm are actinides left behind in the fission product impurities through the PUREX method. Therefore, leaving out Am for a potential production of a mixed oxide (MOX) fuel.
Furthermore, the PUREX method uses a solution containing a reductant to lower the oxidation state of Pu. In the industry, several reductants may be used. The UREX method used reductants acetohydroxamic acid (AHA) or formohydroxamic acid (FHA). These acids will form a decomposition product called hydroxylamine nitrate (HAN). The HAN decomposition product is potentially explosive. It was proven that the HAN decomposition product s responsible for destroying a Hanford site lab in 1997, These decomposition products have the potential for producing catastrophic failure in a recycling plant endangering lives, property, and the environment.
Although various recycling methods are known to the art, all, or most of them suffer from one or more than one disadvantage. There is a need to provide a method for improved recycling of used nuclear fuel.
It is, therefore, the purpose of this invention to provide safe and economical disposal of spent fuel to ensure a stable and economical energy supply for the future. The ROANEX method provides a simpler method for recycling used nuclear fuels.